1. Field of the Invention
This invention relates to an eye direction detecting apparatus for finding an eye direction or gaze point of a user's eye in a finder system.
2. Description of the Prior Art
FIG. 9 shows a view finder of a conventional camera which has a multi-point focus detecting device. The camera has three focus detecting optical systems and three focus detecting zones 10, 11, 12 that correspond to a view of each focus detecting optical system in the view finder. Each of the focus detecting zones 10, 11, 12 indicate a scope of detection of each focus detecting optical system.
The camera has an eye direction detecting device (not shown), which finds a gaze point of the user's eye and judges which focus detecting zone the user looks at. The focus detecting zones coincide with the judgment zones used for judging a position of the gaze point.
When the gaze point is positioned in one of the focus detecting zones, the camera selects the focus detecting optical systems corresponding to the zone in which the gaze point is positioned. The camera detects a focus state of a taking lens with the selected focus detecting optical system, and makes the taking lens focus on the subject in the focus detecting zone. When the gaze point goes out from the focus detecting zone, the camera cancels the selection of the focus detecting optical system.
However, the conventional eye direction detecting apparatus is designed without considering a characteristic of the human's eye.
It is said that if an image is stationary in the same position on a retina, a visual sense is gradually lost away, and then the eye can not sense the image. In order to prevent such a loss of visual sense, the eye is usually moving. One motion is the so-called saccadic eye movement, which has an amplitude of 1 minute and a frequency of 30.about.80 cycles/sec. Also, another motion is the so-called drift, which is a slower random motion of the eye than the saccadic eye movement. Even if a man intends to look at one point, the eye of the man continuously moves.
In cases where the focus detecting zone coincides with the judgment zone, since the gaze point goes out of the judgment zone by an involuntary movement of gaze point, the selection and cancellation occurs very often.
Furthermore, in cases where the user wears contact lenses, the contact lenses move whenever the user's eyes move, resulting in the detection of the gaze point dispersing.